(1) Field of the Invention
The present invention relates to a biometric personal authentication technology, and more specifically to a finger vein authentication technology.
(2) Description of Related Art
As a biometric personal authentication technology using finger vain patterns has come into use, various input devices for vein patterns have been devised. Particularly, many techniques for downsizing the input device and being able to photograph finger vein patterns at the same place every time have been proposed.
In the authentication device using finger vein patterns, authentication is performed according to whether previously registered finger vein patterns and finger vein patterns photographed for the authentication match or not. Accordingly, it is desirable to enable finger vein patterns to be photographed under the same conditions by avoiding influences from ambience when the finger vein patterns are read. If two finger vein patterns to be compared with each other are different in position or angle, the photographed image is corrected by image processing and compared. If the difference is big, the image processing takes a long time and cannot promise appropriate responsibility.
The near-infrared radiation that is used in reading vein patterns affects most among ambience that affects the finger vein pattern to be photographed. The ambience, which is changed by the place of the sun and the like, changes contrast in the finger vein patterns the photographed by near-infrared radiation, resulting in inappropriately photographed finger vein patterns. For example, when too much outside light is coming in, the contrast in the finger vein patterns is lowered and authentication accuracy is also lowered. If the device is adapted to cover a living organism, which is to be photographed, to prevent the near-infrared radiation coming in the photographing unit as the outside light, the state of the living organism cannot be recognized. This gives rise to a problem in that the position of the patterns to be taken is apt to be changed, or such configuration terrifies or worries a user.
A technology to address the problem has also been examined and those described in JP-A-2003-30632, JP-A-2005-301552, and JP-A-2006-99493 have been produced. JP-A-2003-30632 and JP-A-2005-301552 disclose technologies to surround an object of authentication with shielding members to block the outside light such as ceiling lighting from going into an imaging space, or light sources are tilted like a roof with a gap at the top or use transparent shielding members to help a user to locate the finger by allowing the user to check the finger and to alleviate the user's uneasiness. JP-A-2006-99493 discloses a technology to arrange light sources at the sides leaving the top open to alleviate the user's uneasiness and help the user to locate the finger that is an object of authentication.